1. Field of the Invention
This invention relates to an adhesive having excellent adhesiveness to metals, especially to noble metals and noble metal alloys. The adhesive of this invention can be used in many fields such as a medical or electronic material, a precision machine and jewels, for adhering a resin to a metal, especially useful in a dental field.
2. Prior Art
For repairing teeth which are damaged by caries, etc., there has conventionally been practiced a method of adhering a metallic prosthetic material to the teeth. As adhesives for adhering such a metallic prosthetic material to the teeth, dental adhesives in which phosphoric acid ester monomers or carboxylic acid monomers disclosed in Japanese Laid-Open Patent Publication No. 21607/1983 and Japanese Laid-Open Patent Publication No. 293951/1986 are compounded have been used. In applying these adhesives, each adhering surface is pre-treated before coating each prosthetic material with the adhesive in order to increase its adhesive force. Specifically, a tooth is pretreated by an acid aqueous solution typified by phosphoric acid, and on the other hand, the surface of the prosthetic material is sandblasted to make the surface rough.
It has been confirmed that the adhesion by the above method shows an excellent adhesion to base metals such as iron, nickel, chromium, cobalt, tin, aluminum, copper and titanium, and base metal alloys containing the above metals as main components. However, adhesive forces to these noble metal alloys (alloys containing gold, platinum, palladium and silver as main components) are not sufficient. Thus, when noble metals are the object, their adhesiveness is increased by sandblasting the surfaces of noble metal alloys, and further performing the surfaces by tin plating or heating oxidation treatment.
However, procedures of such a tin plating or heating oxidation treatment are complicated. As simpler methods, there was proposed a method of coating surface treating agents containing polymerizable compounds having specified functional groups such as a compound having a thiophosphoric acid group (Japanese Laid-Open Patent Publication No. 138282/1989), a compound having a thiophosphoric acid dichloride group (Japanese Laid-Open Patent Publication No. 117595/1993), a triazinedithione derivative (83254/1989), and a mercaptothiadiazole derivative (Japanese Laid-Open Patent Publication No. 113763/1996) on the surface of a noble metal alloy which is sandblasted in advance. Thus, the procedures were simplified.
However, it is desired to develop an adhesive having sufficient adhesiveness to noble metals and noble metal alloys, which do not always need to surface-treat with a surface-treating agent.